The present invention relates to superconducting electronic devices, and more specifically, to a sum frequency generator in the microwave domain for quantum communication applications.
Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others, even when the particles are separated by a large distance. Instead, a quantum state must be described for the system as a whole. To put it another way, an entangled system is defined to be one whose quantum state cannot be factored as a product of states of its local constituents. In other words, they are not individual particles but are an inseparable whole. In entanglement, one constituent cannot be fully described without considering the other(s). Note that the state of a composite system is always expressible as a sum, or superposition, of products of states of local constituents.